Easy defoaming rotomoulded polypropylene composition and process for the preparation thereof

Abstract

The application discloses a roving plastic polypropylene composition and a preparation method thereof, and belongs to the technical field of the roving plastic process.The composition comprises the following components in parts by weight: 100 parts of polypropylene, 0.2-0.6 parts of an antioxidant, 0.02-0.1 parts of an acid absorbent, 0.05-2 parts of a lubricant and 0.2-0.8 parts of hydrated aluminum oxide.The polypropylene, the antioxidant, the acid absorbent and the lubricant A are uniformly mixed;the lubricant B, the hydrated aluminum oxide and a coupling agent are uniformly mixed after being added into anhydrous ethanol;the remaining polypropylene and the above-mentioned materials are uniformly mixed, are melt-kneaded in a same-direction double-screw extruder and are extruded and granulated;and the granulated material is ground into fine powder to obtain the roving plastic polypropylene composition.The application solves the multiple problems of resin grinding, antioxidation and bubble discharge in the application of the polypropylene in the roving plastic process field.The prepared roving plastic polypropylene composition has less bubbles and superior mechanical properties;and the preparation method is simple, reliable and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of rotational molding technology, specifically relating to a rotational molding polypropylene composition that is easy to defoam and its preparation method. Background Technology

[0002] After half a century of development, rotational molding technology has become increasingly sophisticated, with equipment and processes becoming more refined. Molded products range from tiny doll eyes to large automotive parts and storage tanks holding tens of thousands of liters. In recent years, the domestic market has seen a surge in products manufactured using rotational molding, such as nuclear waste containers, military supplies, one-piece molded car bodies, inspection wells, and telecommunications wells. These products will drive the continuous development of the domestic rotational molding industry. The demand for underground products such as inspection wells, septic tanks, and garbage bins is booming, prompting numerous new manufacturers to enter this sector. The rapid development of the rotational molding industry not only demands creative, functional, and systematic product designs, and large-scale automated, precise, and energy-efficient processing equipment, but will also drive the diversification and functionalization of rotational molding raw materials.

[0003] Rotational molding typically uses polyethylene as the main raw material in 90% of cases. Polypropylene, with its excellent rigidity, heat resistance, chemical stability, and good ESCR performance, has great application potential in the field of rotational molding. It is suitable for manufacturing containers with high temperature resistance requirements, ventilation ducts, and equipment shells with high rigidity requirements, and has broad application prospects in container storage tanks, automotive parts, and other fields.

[0004] In the field of rotational molding, bubble removal is an important research direction. Because rotational molding involves melting and forming under pressureless conditions, air bubbles are often trapped in the powder. Incomplete bubble removal leads to a decrease in the mechanical properties of the product and severely affects its service life. Bubble removal is easier in polyethylene rotational molding than in polypropylene; therefore, research on bubble removal in polypropylene rotational molding is even more necessary.

[0005] In existing technologies, increasing the resin's melting time or temperature provides sufficient time for bubble removal. However, prolonged thermal history leads to material aging. To address this, large amounts of antioxidants are typically added. However, excessive antioxidant addition increases costs and causes yellowing of the finished product. Furthermore, commonly used antioxidants in rotational molding generate bubbles, reducing the product's mechanical properties. Simultaneously, in rotational molding, the raw material must be heated in a mold at 240-280℃ for at least 30-60 minutes, placing extremely high demands on the material's resistance to thermo-oxidative aging. Compared to polyethylene, polypropylene's molecular structure makes it more susceptible to oxidation. The application of polypropylene in rotational molding faces multiple challenges related to resin grinding, oxidation resistance, and bubble removal, resulting in the current lack of application of rotationally molded polypropylene in my country. Summary of the Invention

[0006] To address the multiple challenges faced by polypropylene in rotational molding processes, including resin grinding, oxidation resistance, and bubble removal, this invention provides an easily defoaming rotational molding polypropylene composition and its preparation method. The rotational molding polypropylene composition prepared by this invention produces products with fewer bubbles and superior mechanical properties. Furthermore, the preparation method employed in this invention is simple, reliable, and easy to implement.

[0007] The technical solution adopted by this invention to solve the technical problem is as follows:

[0008] The present invention provides a rotationally molded polypropylene composition that is easy to defoam, comprising the following components in parts by weight:

[0009]

[0010] Preferably, the antioxidant is a phosphite antioxidant.

[0011] Preferably, the phosphite antioxidant is tris(2,4-di-tert-butylphenyl) phosphite.

[0012] Preferably, the acid absorbent is calcium stearate or zinc stearate.

[0013] Preferably, the lubricant is lubricant A and lubricant B; the mass ratio of lubricant A to lubricant B is 1:1 to 1:2.

[0014] Preferably, the lubricant A is di(dodecyl) phthalate.

[0015] Preferably, the lubricant B is Hyper C100.

[0016] Preferably, the hydrated alumina is boehmite with a particle size of 10-60 nm.

[0017] Preferably, the easily defoaming rotational molding polypropylene composition provided by the present invention comprises the following components in parts by weight:

[0018]

[0019] The present invention provides a method for preparing an easily defoaming rotational molding polypropylene composition, which mainly includes the following steps:

[0020] (1) Add half of the polypropylene, antioxidant, acid absorber and lubricant A to a high-speed mixer and stir at 50-90℃ and 1000-1500r / min until they are evenly mixed; lubricant A penetrates into the polypropylene molecules through high-speed stirring under heating.

[0021] (2) Lubricant B, hydrated alumina and coupling agent are added to anhydrous ethanol and then mixed evenly in an ultrasonic mixer. The amount of coupling agent added is 6-10 times that of hydrated alumina.

[0022] (3) Add the remaining half of the polypropylene and the material obtained in step (2) into a high-speed mixer and stir at 300-800 r / min until they are evenly mixed.

[0023] (4) The materials obtained in steps (1) and (3) are melted and mixed in a co-rotating twin-screw extruder and then extruded and granulated.

[0024] (5) Grind the granulated material into fine powder on a grinding mill.

[0025] Preferably, the highest section temperature of the co-rotating twin-screw extruder is 190-230℃, the main engine speed is 150-230 r / min, and the feeding speed is 30-50 r / min.

[0026] Preferably, in the fine powder, 70-85% of the powder is of 40-100 mesh; and in the 40-100 mesh powder, 25-60% is of 40-80 mesh.

[0027] The beneficial effects of this invention are:

[0028] This invention adds lubricants to polypropylene to reduce friction, increase resin fluidity, and improve processing. However, since rotational molding does not involve processing shearing, the type and amount of lubricant used differ from other processes. Some lubricants cause premature plasticization of the resin, leading to prolonged molten material degradation, especially for heat-sensitive materials like polypropylene, which have strict requirements for heating time and temperature. Therefore, lubricant A in this invention takes effect in the early stage of polypropylene plasticization, while lubricant B, which is heat-resistant, takes effect in the later stage. The synergistic effect of lubricants A and B achieves both internal and external lubrication, shortening the plasticization time, resisting material degradation caused by overheating oxidation of polypropylene, and improving the problem of rapid resin aging. Furthermore, the different onset times of these two lubricants are beneficial to the melting and plasticization of the resin. Simultaneously, these two lubricants have antistatic properties, reducing dust attraction and electrostatic discharge in rotationally molded products and improving the impact resistance of rotationally molded polypropylene.

[0029] Excessive use of acid scavengers can cause yellowing of the products after rotational molding. Therefore, in this invention, the amount of acid scavenger added should be strictly controlled. Specifically, in the rotational molding process of this invention, the amount of acid scavenger added to the rotationally molded polypropylene should be reduced by 30-40% to prevent yellowing of the products.

[0030] Because smaller air bubbles formed during rotational molding are more difficult to remove, the resulting microscopic voids in the product after cooling lead to a decrease in its mechanical properties. Therefore, in this invention, pseudoboehmite is specifically selected as the hydrated alumina. When the temperature exceeds 200°C during rotational molding, pseudoboehmite slowly releases water of crystallization, which facilitates the combination of surrounding air bubbles with it, and makes it easier for larger air bubbles to be removed. Detailed Implementation

[0031] The present invention provides a rotationally molded polypropylene composition that is easy to defoam, comprising the following components in parts by weight:

[0032]

[0033] Preferably, the easily defoaming rotational molding polypropylene composition provided by the present invention comprises the following components in parts by weight:

[0034]

[0035] The polypropylene is preferably copolymerized polypropylene, and ethylene, as a copolymer, imparts good toughness to the material. The ethylene content is preferably 4-11% by mass, more preferably 7.8-10.3%; the number average molecular weight is preferably 42,000-47,000, and the molecular weight distribution width is preferably 5.1-6.3.

[0036] The preferred melt flow rate of polypropylene is 6-20 g / 10 min, more preferably 10.0-16.0 g / 10 min, and the preferred test conditions are 230℃ and 2.16 kg.

[0037] Among them, the antioxidant is preferably a phosphite antioxidant.

[0038] Among them, the preferred antioxidant of phosphite is tris(2,4-di-tert-butylphenyl) phosphite.

[0039] The preferred acid absorber is calcium stearate or zinc stearate.

[0040] The lubricant comprises lubricant A and lubricant B; the mass ratio of lubricant A to lubricant B is 1:1 to 1:2; lubricant A is preferably di(dodecyl) phthalate, and lubricant B is preferably Hyper C100, the density of which is preferably 1.1 g / cm³. 3 .

[0041] Hydrated alumina is preferably boehmite, and the particle size is preferably 10-60 nm.

[0042] The present invention provides a method for preparing an easily defoaming rotational molding polypropylene composition, which mainly includes the following steps:

[0043] (1) Add half of the polypropylene (50 parts), antioxidant, acid absorber and lubricant A to a high-speed mixer and stir for 5 minutes at 50-90℃ and 1000-1500r / min until the mixture is uniform. After high-speed stirring under heating, lubricant A penetrates into the polypropylene molecules, effectively reducing the interaction between molecular chains, reducing friction, and promoting the plasticization of polypropylene.

[0044] (2) Add lubricant B, hydrated alumina and coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 minutes. The amount of coupling agent added is 6-10 times that of hydrated alumina. There is no specific limit to the amount of anhydrous ethanol added; it is only used for dilution and will evaporate during the subsequent high-speed stirring process.

[0045] Specifically, hydrated alumina is selected from boehmite. Boehmite has a small particle size and is easy to agglomerate. Under the action of coupling agent and anhydrous ethanol, boehmite is well dispersed. Its high porosity can efficiently adsorb lubricant B.

[0046] (3) Add the remaining half of the polypropylene (50 parts) and the material obtained in step (2) into a high-speed mixer and stir for 2-3 minutes at 300-800 r / min until they are evenly mixed.

[0047] (4) The materials obtained in steps (1) and (3) are melted and mixed in a co-rotating twin-screw extruder and then extruded and granulated.

[0048] Preferably, the highest section temperature of the co-rotating twin-screw extruder is 190-230℃, the main engine speed is 150-230r / min, and the feeding speed is 30-50r / min.

[0049] (5) Grind the granulated material into fine powder on a grinding mill.

[0050] Preferably, in the fine powder, 70-85% of the powder is of 40-100 mesh; and in the 40-100 mesh powder, 25-60% is of 40-80 mesh.

[0051] In this invention, the grinding mill can specifically be a grinding mill used for polyethylene grinding. Typically, during polypropylene grinding, because polypropylene is a poor conductor of heat, shear heat is difficult to remove, and the powder is prone to tailing. Tailing powder has poor flowability when used in rotational molding, resulting in uneven product surfaces. Poorly shaped powder can also cause air bubbles inside the product. This invention effectively solves the problems of oxidation and air bubbles in polypropylene rotational molding. Furthermore, its high compatibility with grinding mills allows downstream manufacturers to perform polypropylene rotational molding without modifying their grinding equipment, eliminating the cost of equipment upgrades and making the promotion of rotational polypropylene more convenient.

[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0053] Example 1

[0054] A method for preparing an easily defoaming rotational molding polypropylene composition specifically includes the following steps:

[0055] (1) Add 50 parts of polypropylene (melt flow rate 10g / 10min (230℃, 2.16Kg), ethylene content 8%), 0.2 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.04 parts of calcium stearate and 0.03 parts of di(dodecyl) phthalate to a high-speed mixer and stir for 5 min at 60℃ and 1000r / min until the mixture is homogeneous.

[0056] (2) Add 0.06 parts Hyper c100, 0.3 parts pseudoboehmite (particle size 10nm) and 2.4 parts aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 min.

[0057] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer and stir for 3 minutes at 500 r / min until they are evenly mixed.

[0058] (4) The materials obtained in steps (1) and (3) are melted and mixed in a co-rotating twin-screw extruder and then extruded and granulated. The highest temperature of the co-rotating twin-screw extruder is 230°C, the main engine speed is 200 r / min, and the feeding speed is 30 r / min.

[0059] (5) Grind the granulated material into fine powder on a grinding mill. 85% of the fine powder is 40-100 mesh; and 50% of the 40-100 mesh powder is 40-80 mesh.

[0060] Example 2

[0061] A method for preparing an easily defoaming rotational molding polypropylene composition specifically includes the following steps:

[0062] (1) Add 50 parts of polypropylene (melt flow rate 14 g / 10 min (230 ℃, 2.16 Kg), ethylene content 8.6%), 0.3 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.05 parts of calcium stearate and 0.05 parts of di(dodecyl) phthalate to a high-speed mixer and stir for 5 min at 50 ℃ and 1000 r / min until the mixture is homogeneous.

[0063] (2) Add 0.08 parts Hyper c100, 0.5 parts pseudoboehmite (particle size 30nm) and 4.0 parts aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 min.

[0064] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer and stir for 3 minutes at 300 r / min until they are evenly mixed.

[0065] (4) The materials obtained in steps (1) and (3) are melted and mixed in a co-rotating twin-screw extruder and then extruded and granulated. The highest temperature of the co-rotating twin-screw extruder is 200℃, the main engine speed is 190r / min, and the feeding speed is 40r / min.

[0066] (5) Grind the granulated material into fine powder on a grinding mill. 85% of the fine powder is 40-100 mesh; and 60% of the 40-100 mesh powder is 40-80 mesh.

[0067] Example 3

[0068] A method for preparing an easily defoaming rotational molding polypropylene composition specifically includes the following steps:

[0069] (1) Add 50 parts of polypropylene (melt flow rate 9 g / 10 min (230℃, 2.16 Kg), ethylene content 10.3%), 0.25 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.03 parts of zinc stearate and 0.1 parts of di(dodecyl) phthalate to a high-speed mixer and stir for 5 min at 50℃ and 1500 r / min until the mixture is homogeneous.

[0070] (2) Add 0.1 parts Hyper c100, 0.2 parts pseudoboehmite (particle size 30nm) and 1.6 parts aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 min.

[0071] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer and stir for 3 minutes at 500 r / min until they are evenly mixed.

[0072] (4) The materials obtained in steps (1) and (3) are melted and mixed in a co-rotating twin-screw extruder and then extruded and granulated. The highest temperature of the co-rotating twin-screw extruder is 230°C, the main engine speed is 190 r / min, and the feeding speed is 50 r / min.

[0073] (5) Grind the granulated material into fine powder on a grinding mill. In the fine powder, 72% of the powder is of 40-100 mesh; in the 40-100 mesh powder, 55% is of 40-80 mesh.

[0074] Example 4

[0075] A method for preparing an easily defoaming rotational molding polypropylene composition specifically includes the following steps:

[0076] (1) Add 50 parts of polypropylene (melt flow rate 15 g / 10 min (230 ℃, 2.16 Kg), ethylene content 7.8%), 0.4 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.02 parts of calcium stearate and 0.8 parts of di(dodecyl) phthalate to a high-speed mixer and stir for 5 min at 90 ℃ and 1300 r / min until the mixture is homogeneous.

[0077] (2) Add 0.9 parts Hyper c100, 0.8 parts pseudoboehmite (particle size 60nm) and 6.4 parts aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 min.

[0078] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer and stir for 3 minutes at 300 r / min until they are evenly mixed.

[0079] (4) The materials obtained in steps (1) and (3) are melted and mixed in a co-rotating twin-screw extruder and then extruded and granulated. The highest temperature of the co-rotating twin-screw extruder is 230°C, the main engine speed is 180 r / min, and the feeding speed is 50 r / min.

[0080] (5) Grind the granulated material into fine powder on a grinding mill. 83% of the fine powder is composed of 40-100 mesh particles; and 55% of the 40-100 mesh particles are composed of 40-80 mesh particles.

[0081] Comparative Example 1

[0082] A method for preparing a rotational molding polypropylene composition specifically includes the following steps:

[0083] (1) Add 50 parts of polypropylene (melt flow rate 12g / 10min (230℃, 2.16Kg), ethylene content 8%), 0.2 parts of pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant), 0.04 parts of calcium stearate and 0.03 parts of di(dodecyl) phthalate to a high-speed mixer and stir for 5 min at 60℃ and 1000r / min until the mixture is homogeneous.

[0084] (2) Add 0.06 parts Hyper c100, 0.3 parts pseudoboehmite (particle size 20nm) and 2.4 parts aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 min.

[0085] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer and stir for 3 minutes at 400 r / min until they are evenly mixed.

[0086] (4) The materials obtained in steps (1) and (3) are melted and mixed in a co-rotating twin-screw extruder and then extruded and granulated. The highest temperature of the co-rotating twin-screw extruder is 230°C, the main engine speed is 180 r / min, and the feeding speed is 30 r / min.

[0087] (5) Grind the granulated material into fine powder on a grinding mill. 80% of the fine powder is composed of 40-100 mesh particles; and 55% of the 40-100 mesh particles are composed of 40-80 mesh particles.

[0088] Since the antioxidant used in Comparative Example 1 was hindered phenolic antioxidant 1010, and the other components were the same as in Example 1, the final antioxidant performance of the material was slightly worse, the yellow index of the rotationally molded product was higher, and the density of the rotationally molded product was lower, indicating that there were more air bubbles inside.

[0089] Comparative Example 2

[0090] A method for preparing a rotational molding polypropylene composition specifically includes the following steps:

[0091] (1) Mixing: Add 50 parts of polypropylene (melt flow rate 14 g / 10 min (230℃, 2.16 Kg), ethylene content 9%), 0.3 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.03 parts of calcium stearate and 0.07 parts of glycerol monostearate (lubricant) to a high-speed mixer and stir at 1500 r / min for 3 min until uniform.

[0092] (2) Extrusion granulation: The uniformly mixed material is added to a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest temperature of the co-rotating twin-screw extruder is 210℃, the main machine speed is 200r / min, and the feeding speed is 40r / min.

[0093] Because Comparative Example 2 did not use a combination of two lubricants, A and B, and hydrated alumina, the material after rotational molding had a higher yellow index, more bubbles, and poorer mechanical properties.

[0094] Comparative Example 3

[0095] A method for preparing a rotational molding polypropylene composition specifically includes the following steps:

[0096] (1) Add 50 parts of polypropylene (melt flow rate 12g / 10min (230℃, 2.16Kg), ethylene content 10.0%), 0.25 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.05 parts of calcium stearate and 0.02 parts of di(dodecyl) phthalate to a high-speed mixer and stir for 5 min at 50℃ and 1500r / min until the mixture is homogeneous.

[0097] (2) Add 0.01 parts Hyper c100, 0.2 parts pseudoboehmite (particle size 30nm) and 1.6 parts aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 min.

[0098] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer and stir for 3 minutes at 500 r / min until they are evenly mixed.

[0099] (4) The materials obtained in steps (1) and (3) are melted and mixed in a co-rotating twin-screw extruder and then extruded and granulated. The highest temperature of the co-rotating twin-screw extruder is 230°C, the main engine speed is 190 r / min, and the feeding speed is 50 r / min.

[0100] (5) Grind the granulated material into fine powder on a grinding mill. In the fine powder, 72% of the powder is of 40-100 mesh; in the 40-100 mesh powder, 55% is of 40-80 mesh.

[0101] In Comparative Example 3, the ratio of the two lubricants A and B is not between 1:1 and 1:2, and the total amount is less than that of the present invention, resulting in more air bubbles in the material.

[0102] Comparative Example 4

[0103] A method for preparing a rotational molding polypropylene composition specifically includes the following steps:

[0104] (1) Add 50 parts of polypropylene (melt flow rate 16 g / 10 min (230 ℃, 2.16 Kg), ethylene content 10.0%), 0.3 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.03 parts of calcium stearate and 1 part of di(dodecyl) phthalate to a high-speed mixer and stir for 5 min at 50 ℃ and 1500 r / min until the mixture is homogeneous.

[0105] (2) Add 1.5 parts Hyper c100, 0.5 parts pseudoboehmite (particle size 50nm) and 4.0 parts aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 min.

[0106] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer and stir for 3 minutes at 500 r / min until they are evenly mixed.

[0107] (4) The materials obtained in steps (1) and (3) are melted and mixed in a co-rotating twin-screw extruder and then extruded and granulated. The highest temperature of the co-rotating twin-screw extruder is 230°C, the main engine speed is 190 r / min, and the feeding speed is 50 r / min.

[0108] (5) Grind the granulated material into fine powder on a grinding mill. In the fine powder, 72% of the powder is of 40-100 mesh; in the 40-100 mesh powder, 55% is of 40-80 mesh.

[0109] In Comparative Example 4, the material impact strength deteriorated because the ratio of the two lubricants A and B was not between 1:1 and 1:2, and the total amount was greater than that of the present invention.

[0110] Comparative Example 5

[0111] A method for preparing a rotational molding polypropylene composition specifically includes the following steps:

[0112] (1) Mixing: Add 50 parts of polypropylene (melt flow rate 14 g / 10 min (230℃, 2.16 kg), ethylene content 8.6%), 0.4 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.05 parts of calcium stearate, 0.1 parts of di(dodecyl) phthalate, 0.1 parts of Hyper C100 and 0.2 parts of boehmite (particle size 30 nm) to a high-speed mixer and stir at 1000 r / min for 3 min until uniformly mixed.

[0113] (2) Extrusion granulation: The uniformly mixed material is added to a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest temperature of the co-rotating twin-screw extruder is 230℃, the main machine speed is 200r / min, and the feeding speed is 40r / min.

[0114] Comparative Example 5 did not use the preparation method of this invention, but only used common mixing and granulation, resulting in more air bubbles and a higher yellow index in the material after rotational molding.

[0115] Experimental Example 1

[0116] The products obtained in Examples 1-4 and Comparative Examples 1-5 were tested according to the following standards:

[0117] Melt mass flow rate (MFR): conducted according to GB / T 3682.1-2018, with a test temperature of 230℃ and a load of 2.16 kg;

[0118] The notched impact strength of simply supported beams shall be tested in accordance with GB / T 1043-2008;

[0119] Tensile properties were tested according to GB / T1040.2-2006, using type I specimens, with a tensile speed of 50 mm / min;

[0120] Bending performance was tested according to GB / T 9341-2008;

[0121] Oxidation induction time (OIT): Performed according to GB / T19466.6-2009, with a heating rate of 20℃ / min and a temperature of 200℃.

[0122] Yellow Index: Tested according to ASTM E313-2010. The sample used for testing the yellow index is a 2mm thick square piece, and the injection temperature is 200℃.

[0123] The rotational molding products in the examples and comparative examples were made using the following rotational molding process:

[0124] Heating temperature: 240℃ Heating time: 1200 seconds

[0125] Cooling time: 900 seconds Cooling method: Air cooling

[0126] Table 1. Dosage of each component and performance data of the examples.

[0127]

[0128]

[0129] Table 2. Dosage of each component in the comparative example and performance data of the comparative example.

[0130]

[0131] In summary, based on the above test results, it can be seen that the easily defoaming rotational molding polypropylene composition of the present invention is superior to the prior art in terms of tensile yield stress, nominal strain at break, notched impact strength of simply supported beam, flexural modulus of elasticity, oxidation induction time, yellow index of the composition, yellow index of the rotational molding product, density of the composition, and density of the rotational molding product.

[0132] This invention discloses an easily defoaming rotational molding polypropylene composition and its preparation method. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The product of this invention has been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the product described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

Claims

1. A rotationally molded polypropylene composition that is easy to defoam, characterized in that, It includes the following components by weight: 100 parts of polypropylene; Antioxidant 0.2-0.6 parts; Acid absorbent 0.02-0.1 parts; Lubricant 0.05-2 parts; 0.2-0.8 parts of hydrated alumina; The antioxidant is a phosphite antioxidant; the lubricant is lubricant A and lubricant B; the mass ratio of lubricant A to lubricant B is 1:1-1:2; lubricant A is di(dodecyl) phthalate, and lubricant B is Hyper C100; The method for preparing the easily defoaming rotational molding polypropylene composition includes the following steps: (1) Add half of the polypropylene, antioxidant, acid absorber and lubricant A into a high-speed mixer and stir at 50-90℃ and 1000-1500r / min until they are evenly mixed; after high-speed stirring under heating, lubricant A penetrates into the polypropylene molecules. (2) Lubricant B, hydrated alumina and coupling agent are added to anhydrous ethanol and then mixed evenly in an ultrasonic mixer. The amount of coupling agent added is 6-10 times that of hydrated alumina. (3) Add the remaining half of the polypropylene and the material obtained in step (2) into a high-speed mixer and stir at 300-800 r / min until they are evenly mixed. (4) The materials obtained in steps (1) and (3) are melt-mixed in a co-rotating twin-screw extruder and then extruded and granulated. (5) Grind the granulated material into fine powder on a grinder.

2. The easily defoaming rotational molding polypropylene composition according to claim 1, characterized in that, The phosphite antioxidant is tris(2,4-di-tert-butylphenyl) phosphite.

3. The easily defoaming rotational molding polypropylene composition according to claim 1, characterized in that, The acid absorber is calcium stearate or zinc stearate.

4. The easily defoaming rotational molding polypropylene composition according to claim 1, characterized in that, The hydrated alumina is boehmite with a particle size of 10-60 nm.

5. The easily defoaming rotational molding polypropylene composition according to claim 1, characterized in that, It includes the following components by weight: 100 parts of polypropylene; Antioxidant 0.2-0.3 parts; 0.03-0.05 parts of acid absorbent; Lubricant 0.05-2 parts; 0.2-0.5 parts of hydrated alumina.

6. The method for preparing the easily defoaming rotational molding polypropylene composition according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Add half of the polypropylene, antioxidant, acid absorber and lubricant A into a high-speed mixer and stir at 50-90℃ and 1000-1500r / min until they are evenly mixed; after high-speed stirring under heating, lubricant A penetrates into the polypropylene molecules. (2) Lubricant B, hydrated alumina and coupling agent are added to anhydrous ethanol and then mixed evenly in an ultrasonic mixer. The amount of coupling agent added is 6-10 times that of hydrated alumina. (3) Add the remaining half of the polypropylene and the material obtained in step (2) into a high-speed mixer and stir at 300-800 r / min until they are evenly mixed. (4) The materials obtained in steps (1) and (3) are melt-mixed in a co-rotating twin-screw extruder and then extruded and granulated. (5) Grind the granulated material into fine powder on a grinder.

7. The preparation method according to claim 6, characterized in that, The highest temperature of the co-rotating twin-screw extruder is 190-230℃, the main engine speed is 150-230 r / min, and the feeding speed is 30-50 r / min.

8. The preparation method according to claim 6, characterized in that, Of the fine powder, 70-85% is composed of powder with a mesh size of 40-100; and of the powder with a mesh size of 40-100, 25-60% is composed of powder with a mesh size of 40-80.

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